Such a fueling device serves to fill the cryogenic thrusters with propellants and to do so up to the moment of lift-off. This constraint leads to a certain number of technical difficulties, since the pipework connecting the ground to the launcher must be reliably disconnected at the moment of launch, and this must take place without modifying the trajectory of the launcher and without interfering with the equipment that remains on the ground or the equipment that is on board the cryogenic stage or any other stage of the launcher.
Conventionally, cryogenic arms are used that are fitted with valve plates. These valve plates, which provide an on-board/ground connection, enable various filling and pressurizing operations to be performed that are needed for launch checking and preparation. They comprise an on-board plate and a ground plate, both of which are fitted with valves that serve to close the hydraulic and pneumatic circuits on board and on the ground (for filling, and purging/degassing).
These independent plates are mechanically connected together during the production stage and they are mounted together on the launcher during the integration stage. They are mechanically and permanently separated at the end of the launch countdown shortly before operation is checked in a manner that might potentially lead to the launch being aborted.
This unlocking between the ground and on-board plates is performed by using unlocking actuators that have two portions that are made movable relative to each other when pressure is applied to the actuator. These portions are fastened respectively to the ground plate and to the on-board plate so they are moved apart from each other when the unlocking actuators are pressurized. Thereafter, as a result of the weight of the plates and of the hoses that are attached thereto and as a result of the traction exerted by a dedicated extraction cable while the launcher is climbing, the ground and on-board plates pivot about a hinge pin that connects them together until the hinge pin is released, thereby leading to the ground and on-board plates being separated.
Thus, in the event of a launch being aborted as a result of the engines malfunctioning, such that the launcher has not climbed, an irreversible separation has occurred to the ground/on-board connection, with the ground pipework being dropped.
Consequently, with such equipment, since reconnection is not possible, it is no longer possible to empty the launcher in normal manner and it is necessary to change the ground/on-board connection once the launch has been aborted.
Such a change of the ground/on-board connection includes replacing the valve plate and involves a complete reconfiguration of the propellant circuit, including emptying the tanks, which can take a very large amount of time (about one week).
In addition, the operation of disengaging the cryogenic arms during a launch is difficult to perform: if the arm is retracted a little too late, even though that does not unbalance the launcher, there exists a risk of damaging the fueling device both in the ground installations and in the installations on board the launcher.